In this paper, we show the dynamic behaviors of a sheet plasma and the corresponding release of blob-like plasmas to the periphery of the sheet based on observation with a high-speed camera. We found that the plasma column moves in a transverse direction reciprocally when injecting a small amount of Ar gas to the He plasma from the plasma source region. The motion continued periodically at a frequency of ∼5 kHz. The frequency of the plasma column motion decreased with increasing Ar gas flow rate and increasing magnetic field. The mechanism of the transverse motion is discussed. Furthermore, in response to the reciprocating motion, release of a blob-like plasma was observed. The differences in the behavior of the released plasma compared with the other linear devices are discussed. KEYWORDS linear device, plasma dynamics, sheet plasma 1 How to cite this article: Onda T, Kajita S, Iijima T, Tonegawa A, Ohno N and Tanaka H. Transverse motion of a plasma column in a sheet plasma. Contrib. Plasma Phys.

We have investigated the particle flux flowing into the axisymmetric end-target in the transient state from attached to detached divertor conditions in the linear plasma device NAGDIS-II. In the transient state, a dramatic decrease of the mean particle flux and a large-amplitude fluctuation with negative and positive spikes were observed. We have analyzed the fluctuation with a newly suggested analysis technique: pre-multiplied cubic spectrum with the wavelet transform. Analysis result indicates that these spikes consist of a few kilohertz components.

In linear plasma devices, blob-like cross-field transport is enhanced especially in detached plasmas. Formation of blob-like plasmas in the linear plasma device NAGDIS-II was observed using a fast framing camera, and the mode analysis was conducted using the emission from the plasma column. From the Fourier analysis, it was seen that plasma instability was enhanced before the ejection of blob-like plasmas from the plasma column. It was found that blob-like plasmas are generated at the peripheral region of the plasma column associated with low mode number (m = 0 -2) plasma instability inside the plasma column.